Power electronics, such as power supplies, solar energy panels, and electric vehicles, often utilize power switch devices. For example, power switch devices may be utilized in AC to DC converters, DC to AC converters, DC to DC converters, and AC to AC converters within the power electronic devices. However, many challenging design specifications have to be met in order to provide better performance. These design specifications include excellent current-voltage switching capability and quick charge recovery. Also, most consumer electronics require normally-off operation.
In many applications, power switch devices are formed from a depletion mode transistor provided in cascode with enhancement mode transistor. The depletion mode transistor is utilized as the high-voltage device while the enhancement mode transistor provides voltage shifting to turn off the depletion mode transistor. For instance, a power switch device has been formed from an enhancement mode MOSFET in a cascode with a depletion mode junction gate field effect transistor (JFET) or a metal-semiconductor field effect transistor (MESFET). However, the switching speed of the depletion mode JFET or MESFET switch is limited by its current and voltage switching capability and thus limits the switching speed of the power switch device for high voltage applications (>300V).
Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are more conducive to high speed and high voltage switching due to their higher peak electron velocity and wider bandgap as compared to other technologies. Nevertheless, all-GaN solutions are very expensive. In contrast, other solutions have formed a Gallium Arsenide (GaAs) enhancement mode transistor in cascode with a depletion mode GaN HEMT. Unfortunately, the lower gate to source threshold voltage characteristic of the lower bandgap GaAs E-mode device results in a Schottky turn-on voltage at significantly lower input voltages. This premature Schottky gate forward turn-on can degrade and produce adverse switching transients leading to poorer power efficiency.
Accordingly, what is needed is a less expensive arrangement for a power switch device that has high current switching capability while maintaining a higher Schottky breakdown voltage.